1. Field of the Invention
The invention relates to bulldozer blade control mechanisms.
2. Description of the Related Art
A bulldozer blade is generally mounted on the chassis of the vehicle so that it can be actuated by hydraulic cylinders in at least three distinct motions: blade tilt, up and down, and blade angle. In the largest bulldozers, blade pitch is also a controllable motion. Simplified versions of hand operated control mechanisms to accomplish these hydraulically actuated motions has been sought after for quite a while.
U.S. Pat. No. 3,700,044, issued to Berg, discloses a single lever control which pivots on two axes to control the pitch (e.g. the upper portion of the blade is moved fore or aft relative to the lower portion of the blade) and tilt (raising one end of the blade relative to the other end). Berg teaches that angling (moving one end of the blade forward relative the other end) is best accomplished by a separate lever.
U.S. Pat. Nos. 3,795,280 and 3,854,380, issued to Casey, disclose what is described as "a three-way lever control" for hydraulic control valves. However, the "lever" is able to control only two valves; the third is controlled by a second lever arm, attached to the "lever" which actuates a solenoid switch. It is clear that this "lever" is capable of operating only in two distinct planes, x and y.
U.S. Pat. No. 3,747,472, issued to Knutson, discloses the advantages offered by a system that can actuate three hydraulic controls by a single lever. However, rather provide a mechanical linkage that accomplishes the task, Knutson requires a complicated force amplifier system using push pull cables. The use of this complex system results in extra cost and reduced reliability.
A single lever blade control apparatus that is capable of operating in three mutually perpendicular planes to activate three independent hydraulic valves controlling a bulldozer blade is not found in the prior art.